The invention relates to a windshield wiper drive unit having a drive motor and a gear for transmitting a rotary motion of the motor to the shaft of a windshield wiper, having at least one sensor for detecting a position of the shaft, and having a control circuit, which receives a detection signal of the sensor and has one or more inputs for receiving operating signals that define a desired operating state of the windshield wiper and is arranged to control a sequence of motions of the shaft as a function of the operating signal received.
This control circuit is responsible for all the relevant functions of the windshield wiper, such as wiping at different speeds, intermittent wiping with various intervals between wiping phases, triggering of a pump for a windshield washer fluid, and so forth. The at least one sensor is used to obtain the information required for controlling the sequence of motion of the wiper from the current position of the wiper, that is, whether the wiper is moving across a position at which a switching operation of the control circuit is required, whether the wiper is moving at the required speed, or whether the wiper has become stuck, for instance from an overload of snow on the window.
The more manifold and complex the possible operating states of the wiper are, the more sensors are generally necessary for controlling it, and the more information has to be exchanged between sensors, control circuit and motor. This requires a large number of lines between the motor and sensor or sensor on the one hand and the control circuit on the other. If the part of the control circuit that supplies current to the wiper operates in clocked fashion, then a complicated interference suppressor for the signals exchanged among the sensors, control circuit and motor is additionally required.
By the present invention, a windshield wiper drive unit of the type defined at the outset is created which enables simple signal transmission, with little vulnerability to interference, between the sensor or sensors, the control circuit, and the drive motor. Because these three components are in fact combined into an integral component unit, the signal paths between them are shortened considerably, and the introduction of external interference into the signal lines is reduced considerably. The integral component unit can be shielded off from external interference as a whole without difficulties, for example by a compact metal housing.
From outside, along with the requisite supply voltages, all that it receives is operating signals with which a driver of the vehicle specifies a desired operating state of the windshield wiper. These operating signals vary extremely seldom, compared to the detection signals of the sensor or sensors, and accordingly their transmission is has very low susceptibility to interference.
Further characteristics and advantages of the invention will become apparent from the ensuing description of an exemplary embodiment.